Oxalyl chloride

Structural formula
General
Surname	Oxalyl chloride
other names	Oxalic acid dichloride Oxalyl dichloride
Molecular formula	C 2 Cl 2 O 2
Brief description	colorless liquid with a pungent odor
External identifiers / databases
CAS number 79-37-8 EC number 201-200-2 ECHA InfoCard 100.001.092 PubChem 65578 Wikidata Q413566
properties
Molar mass	126.93 g mol −1
Physical state	liquid
density	1.48 g cm −3 (20 ° C)
Melting point	−12 ° C
boiling point	63-64 ° C
Vapor pressure	200 hPa (20 ° C)
solubility	Decomposes in water soluble in diethyl ether , chloroform and benzene
Refractive index	1.434 (13 ° C)
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 260-331-314-335 EUH: 014-029 P: 280-301 + 330 + 331-304 + 340-305 + 351 + 338-308 + 310-402 + 404
Thermodynamic properties
ΔH f 0	−367.6 kJ mol −1
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . Refractive index: Na-D line , 20 ° C

Oxalyl chloride is a chemical compound with the molecular formula (COCl) ₂ . It is an extremely aggressive and pungent smelling chemical. It is the diacid chloride of oxalic acid from which it is also made. The colorless liquid is accessible from anhydrous oxalic acid and phosphorus pentachloride .

properties

Oxalyl chloride is a colorless liquid that fumes in moist air due to hydrolysis . It is highly volatile, but when it evaporates / evaporates, a residue of hydrolyzed oxalic acid is often left behind, which is created by the reaction with the humidity. The thermal decomposition leads to the formation of phosgene and carbon monoxide .

${\displaystyle \mathrm {(COCl)_{2}\rightarrow COCl_{2}+CO} }$

use

In Swern oxidation , a selective method for the production of aldehydes from primary alcohols , oxalyl chloride is used to activate the oxidizing agent DMSO . It is used to produce the corresponding chloralkanes or acid chlorides from sensitive alcohols and acids. Despite the lower reactivity compared to other halogenating agents, it is used because of the better selectivity .

It is also required to produce oxalic acid esters that cannot be obtained directly from oxalic acid, for example phenyl oxalates for peroxychemiluminescence.

${\displaystyle \mathrm {2\ RCH_{2}OH+(COCl)_{2}\longrightarrow } }$ ${\displaystyle \mathrm {RCH_{2}OC(O)C(O)OCH_{2}R+2\ HCl} }$

Accidents

On March 15, 2000, an Airbus 330 operated by Malaysia Airlines suffered a total write-off when oxalyl chloride leaked from incorrectly declared canisters. Five airport employees suffered poisoning while reloading the cargo.

Individual evidence

1. ↑ ^{a b c d e f g h} Entry on oxalyl dichloride in the GESTIS substance database of the IFA , accessed on January 9, 2019(JavaScript required) .
2. ↑ Entry on oxalyl chloride. In: Römpp Online . Georg Thieme Verlag, accessed on March 4, 2014.
3. ↑ CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
4. ↑ David R. Lide (Ed.): CRC Handbook of Chemistry and Physics . 90th edition. (Internet version: 2010), CRC Press / Taylor and Francis, Boca Raton, FL, Standard Thermodynamic Properties of Chemical Substances, pp. 5-21.
5. ↑ VN Khabashesku, B. Pödör, T. Székely, AK Mal'tsev, OM Nefedov: Mass spectrometric study of thermal decomposition of oxalyl chloride at low pressures in Bulletin of the Academy of Sciences of the USSR, Division of Chemical Science 32 (1983 ) 722-725, doi : 10.1007 / BF00953463 .
6. ↑ Aircraft accident data and report in the Aviation Safety Network (English)